Discipline and poker

[GrassHopperAA]

I know poker takes discipline, especially when making a living at it. I wanted to ask in what ways do you need to apply discipline. Some ways I can think of off the top of my head are:

Playing within your roll
Stepping away when you're not on your A game
Not playing table games (in vegas)
Taking time to study the game and analyze your play

What else is there?